1. Field of the invention
The present invention relates to the dispensing of medicaments and like substances in single drop form generally and, more particularly, to a novel method and means for dispensing such substances from aerosol containers in metered single drops.
2. Background Art
There are many applications in which it is desirable to dispense accurately metered doses of medicaments and like substances, such as ophthalmic medicaments. Most solutions available for single drop usage are aqueous base solutions which are dispensed from squeeze-base dropper packages. A substantial limitation of such packages is control of the number and size of drops dispensed from the dropper and the maintenance of sterility of the contents of the packages. The former problem arises from the fact that the dropper must be squeezed with pressure within a relatively narrow range of magnitude in order to achieve a single drop. The latter problem arises from the fact that there is no positive sealing of the outlet of the package, as, typically, the contents are exposed while the dropper is removed from the package, the dropper is exposed during use, and air is drawn into the package to replace solution removed. In some cases, remedying the latter problem requires the addition of preservatives to the ingredients.
Aerosol packages have been employed for the dispensing of medicaments in spray form for topical use. Additionally, such aerosol packages have been employed for the dispensing of such substances as perfumes, mouth fresheners, and make-up materials. They have also been widely used for dispensing inhalation drugs where medicaments in suspension or solution are propelled with large quantities of propellant to keep the particle sizes small in order to effectively enter the lungs of the user. The latter, for example, advantageously uses the mucous membrane in the nose, buccal cavity, and the lungs as a vehicle to introduce drugs into the blood stream. For some products, such as make-up foam mousse, a stable foam is desirable and to obtain the same, water-insoluble propellants such as isobutane or propane are used with the water-based ingredients to yield a stable foam.
Aerosol packages offer the advantages of positive closure of the package after use and no air is drawn into the package to replace the ingredients dispensed; therefore, in many cases, there is no need for the addition of preservatives to the ingredients. An additional advantage of aerosol packages is that they are highly tamper-proof.
Many aerosol packages continue to deliver product as long as the aerosol valve is actuated; however, devices for the delivery of metered aerosol sprays are well known and are available, for example, from Valois, Le Prieure BP G-27110 Le Neubourg, France, which furnishes metering valves to provide a measured quantity of the material being dispensed in a spray form wherein the metering valve restricts the amount of material emitted from the aerosol package. These valves are used predominantly for inhalation drugs. Such devices typically employ propellants which are highly water-insoluble and, as noted above, are provided in a high proportion relative to the effective material being dispensed. A substantial limitation of such delivery systems is that the high velocity of the spray, resulting from the high ratio of propellant, may be irritating and a medicament or similar substance in spray form is difficult to direct to the desired point of use. It is even more difficult to assure that the entire quantity of substance is delivered to that desired point of application. Another limitation of such systems is that they are unsuitable for the delivery of ophthalmic preparations because of the potential irritation of the eye by the nature of the propellants used and by the substantial chilling effect caused by the expansion of the large quantity of propellants used.
It is desirable that there be provided an aerosol-type delivery system which has the advantages of maintenance of sterility of substances, yet avoids the disadvantages thereof. As noted above, presently known metered aerosol delivery systems provide the applied substance in spray form.
Accordingly, it is a principal object of the present invention to provide a method and means for metered single-drop aerosol dispensing which permit delivery of a selected quantity of a substance to a selected site in essentially drop form.
Another object of the invention is to provide such method and means that permit the delivery of such substances while maintaining sterility thereof.
Other objects of the invention, as well as particular advantages and features thereof, will be elucidated in, or apparent from, the following description and the accompanying drawing figures.